Demand Limiting; Linkage - Carrier TruVu VVTZC-E2 Installation And Startup Manual

Wiring inputs and outputs

Demand limiting

Demand limiting is a cost-saving strategy to reduce energy consumption. The strategy expands the setpoints when
the system reaches one of 3 levels of consumption. With the expanded setpoints, the equipment works less,
thereby saving energy.
If the TV-VVTZC-E2 receives a demand limit signal through the network, it expands its setpoints based on the
demand level. The default amounts are:
•
Demand Level 1: 1 °F (.6 °C)
•
Demand Level 2: 2 °F (1.1 °C)
•
Demand Level 3: 4 °F (2.2 °C)

Linkage

The i-Vu Control System uses linkage to exchange data between the zone terminals and their air source to form a
coordinated HVAC system. The system's air source controller, zone controllers, and bypass controller are linked so
that their data exchange can be managed by one zone controller configured as the VVT Master.
The VVT Master gathers the following information from the slave zone controllers: occupancy status, setpoints,
space temperature, relative humidity, CO
performs mathematical calculations and algorithms on the data and then sends the composite information to the
air source. The VVT Master receives information from the air source such as mode, supply air temperature, and
outside air temperature, if present, and passes that information to all linked controllers.
The VVT Master determines system operation by prioritizing heating and cooling requirements from all the zones
based on their occupancy and demand. The VVT Master scans the system continuously to determine if any zones
are occupied. Occupied zones are a higher priority than unoccupied zones. The VVT Master evaluates all the
occupied zones' heating or cooling demands and sends a request to the air source for:
•
Cooling, if the number of occupied zones with cooling demands exceeds the number of occupied zones with
heating demands, and the demand is greater than or equal to the number of configured Linkage Callers.
•
Heating, if the number of occupied zones with a heating demand exceeds or is equal to the number of
Linkage Callers.
A Linkage caller zone is determined by two user-adjustable parameters, A binary value is used to inhibit any
individual zone from becoming a heat or cool caller.
If Inhibit Cooling Call from this zone? is set to Yes, then this zone is ignored when determining total cooling calls.
Likewise, if Inhibit Heating Call from this zone? Is set to Yes, then this zone's heating requirement will be ignored.
Next, if both of the above are set to No, then the amount of zone temperature deviation from setpoint determines
when a zone becomes a caller. For cooling, this is determined by the amount of the yellow setpoint band. A zone
must exceed this band and enter into the orange band to become a cooling caller. The yellow band by default is
1 °F (.5 °C), therefore the space temperature must exceed the cooling setpoint by more than 1 °F (.5 °C) to
be counted as a cooling request.
The light blue band is used to determine the deviation required to become a heating caller. It is also set to a
default value of 1 °F (.5 °C), but you can adjust it.
If no zones are occupied, or no occupied zones require heating or cooling, the VVT Master performs the evaluation
described above for the unoccupied zones.
The VVT Master then gathers the following information and sends it to the air source:
•
The setpoints and space temperature from the zone with the greatest demand for the requested air source
mode (heating or cooling). (This zone is called the reference zone.)
•
The system occupancy status
•
Most open damper position from any zone
•
RH and CO
2
TruVu™ VVTZC-E2
Installation and Start-up Guide
level, damper position, and optimal start data. The VVT Master
2
values (if applicable)
64
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